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Spectroscopy on the EBIT facility provides information that can be divided into four general categories.

  1. Position of the spectral lines. Crucial for the precise determination of the energy levels, for line identification and line blends, as well as tests of relativity and quantum electrodynamics.
  2. Intensity of the spectral lines. It allows the measurement of the electron-ion interaction cross sections. The cross section measurements include electron-impact excitation, dielectronic recombination, innershell ionization, and resonance excitation. The intensity information also allows the study of polarization phenomena.
  3. The temporal evolution of the spectral lines. It allows the study of transient phenomena such as innershell ionization and line emission by radiative electron capture. It also allows the study of radiative lifetimes of long-lived excited states.
  4. Line shape information. It allows a determination of the temperature of the trapped ions from the thermal doppler broadening and thus provides basic information on the trap performance.

The electron beam energy provides yet another dimension to the range of experimental conditions EBIT can access. The beam is quasi mono-energetic with an energy spread of 30-50 eV FWHM and can be changed at a rate of 50 V/ns, i.e., at a rate faster than that of the electron-ion interaction process. As a result, we can use EBIT to make an ion at one energy and probe it with electrons at a second energy, selecting the electron-ion interaction process of interest. The line formation processes in EBIT are thus very different from those in a plasma, where virtually all processes occur simultaneously.

The information gathered by our spectroscopic measurements is used to determine precisely atomic and nuclear properties, to measure electron-ion interaction cross sections, and to provide atomic data needed in the spectral modeling of astrophysical observations, as well as in fusion and x-ray laser research.

Atomic Data for Fusion Plasmas and X-ray Lasers

Accurate atomic data are the foundation for developing reliable spectroscopic diagnostic of high temperature plasma generated by magnetic fusion devices and by high-power lasers in inertial confinement fusion (ICF) research. They are also paramount to developing short-wavelength X-ray lasers. Our spectroscopy measurements play a crucial role in establishing such an accurate and reliable atomic data base.

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